This is a phrase those of us, shall we say, a certain age, will have heard - especially those of us who have parents who grew up through or were part of WW2!
Not that its part of our collective memory - just was an observation at that time borne out of hard and difficult times - for all!!! I will qualify that a bit - as my Dad told me...if the US hadn't come in when they did - we would have been stuffed - so the collective view is "thank-you!!!" It was just a bit of humour which I dare say - was needed desperately at that time!